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Thread: how to find an element in an array

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    Default how to find an element in an arrayList

    Hi guys,

    Im trying to write a very small and simple method that will find an element from a arrayList and return it. the list contains instances of a class called People. I tried using the indexOf method to find the index of the desired element and then the get() method to return the element using the previously found index.

    I just keep getting the java.lang.ArrayIndexOutOfBoundsException: -1 error.


    the code I have is:

    public Names findPerson(String aString)
       {
          int personIndex = people.lastIndexOf(aString);
          return people..get(personIndex);
       }

    any help is much appreciated.
    Last edited by humdinger; April 9th, 2010 at 05:15 AM.


  2. #2
    Super Moderator helloworld922's Avatar
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    Default Re: how to find an element in an array

    any of the indexOf methods (first, last, etc.) return -1 if the string was not found.

  3. The Following User Says Thank You to helloworld922 For This Useful Post:

    humdinger (April 9th, 2010)

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    Default Re: how to find an element in an array

    ok thankyou for the advice, i know the string is in there so I will do some testing on this later. Does anyone have any ideas?

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    Default Re: how to find an element in an array

    Have you considered using Hashtables?

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    Default Re: how to find an element in an array

    Hi, i thought about tthat but as I only have an arrayList with all the People objects stored in it Im not sure it would work as I have nothing to use as keys. I will definately look into it in more detail later though. Im unable to do it now as im at work & not with my computer. Thankyou for the advice

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    Default Re: how to find an element in an array

    Doesn't your People object has a id? something along the way of peopleId.

    I'm using a Hastable with User objects in it, and my userid is the key in the Hashtable, that way I can easy find users based on their id

  8. The Following User Says Thank You to Bryan For This Useful Post:

    humdinger (April 9th, 2010)

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    Default Re: how to find an element in an array

    ok great il give it a try when i get home
    thanks again
    Last edited by humdinger; April 9th, 2010 at 10:46 AM.

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    Default Re: how to find an element in an array

    it works!!! thankyou Brian, I cant believe I didnt think of that before! silly me

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    Default Re: how to find an element in an array

    No problem, I just started learning Java and also had to deal with the same problem that you had.

    I first solved it by making my own get(id) and then iterate through the array and comparing the id with the object->getID(). But I refused to believe Java didn't had a better solution for this so I went through the documentation and found it

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